Access to clean drinking water is essential to human health. Unfortunately, a large portion of the world population lives in developing areas where clean drinking water is not available. However, many of these same areas have access to a virtually unlimited supply of salt water, e.g. from nearby oceans. This salt water can be desalinized to provide drinking water.
Conventional land-based desalinization techniques rely heavily on electricity, however, which is another commodity in short supply in the developing world. Conventional desalination techniques also have the disadvantage of generating large quantities of waste brine. It can be difficult and costly to dispose of waste brine.
One conventional process for desalinization uses a series of effects. Each effect is a separate chamber at an incrementally lower pressure and temperature than the last. Raw water is passed into the first effect and heated to boiling. The steam resulting from the evaporation within the first effect is then used to heat raw water in the second effect. This process is repeated and the steam is eventually condensed into a stream of desalinized water.
Conventional desalinization processes have been implemented in a variety of locations. Such processes have been used, for example, to provide drinking water in coastal areas with low rainfall. Such processes also have been used on ocean vessels. Conventional shipboard desalinization systems typically are sized for supplying sufficient water for the crew and any passengers over the expected length of a voyage. These systems require substantial maintenance and cannot be operated beyond their design capacities in a cost-effective manner.
There is a great need for simple desalinization and purification systems that use readily available and inexpensive sources of energy, that can be operated cost effectively on a large scale and that can be adapted for on-ship installation. Since waste brine disposal requirements often make desalinization cost-prohibitive, there also is a need for desalinization systems that do not produce waste brine in significant amounts.